Machines designed to perform electrical machining are commonly equipped with a power supply for providing machining energy to a fluid-filled machining gap formed between a pair of electrodes, one of which may be a tool electrode and the other a workpiece. In EDM the power supply has been adapted to furnish the machining gap with machining energy in the form of high-frequency discrete pulses and the use of the high-frequency pulsed energy has been found to be highly effective in other electrical machining processes as well where smooth direct-current gives rise to machining difficulties or inefficiency. In conventional EDM and other machining power supply circuit arrangements, machining power pulses are produced in a unit (power supply unit) provided separately from the machine proper which carries mechanical components and the work vessel in which the machining gap is defined between the tool electrode and the workpiece. The separate power supply unit has been adapted to package in its cabinet all principal electrical components required to produce at its output a succession of unidirectional power pulses of a predetermined polarity relative to the tool electrode and the workpiece. In an attempt to obtain machining pulses of an increased peak current or amplitude required to attain an enhanced removal rate and efficiency, the power supply unit sometimes contains an energy-storage capacitor for recurrent charging and discharging; the output of the capacitor is connected to, and hence the power pulses outgoing from the unit are transmitted to, the machining gap by way of an elongated cable or line. As a consequence, stray resistance and inductance included in the cable or line impede transmission of the unidirectional electric power and act to cause a considerable loss of power and distortion of pulse waveform transmitted to the machining gap. It has, therefore, been unavoidable for the material removal to be undesirably limited, for the machining efficiency to be unsatisfactorily low and for the entire power unit to become excessively large and bulky in conventional electrical (discharge) machines. In effect, the conventional design of using an energy storage capacitor in electrical machining art has not been satisfactory to achieve its intended purposes and advantages.